Studies are proposed aimed at confirming preliminary observations indicating that a new experimental model may have been found to induce respiratory distress syndrome in newborn rats. Female rats are fed, from the 6th day of pregnancy, a diet supplemented with N, N-Dimethylethanolamine, a natural phospholipid base present only in trace amounts in mammalian tissues. Pregnancy and delivery proceed normally, but the pups die within the first 36 hours. Preliminary histopathological observations have revealed the presence in lungs of the pups of alterations mimicking those seen in human infants with acute respiratory distress syndrome. These alterations are accompanied by a low content of surfactant in the lung. Ultrastructural studies will be carried out in order to characterize and better define the nature and significance of the observed pulmonary alterations. At the same time, biochemical studies will be performed in order to probe the metabolic basis of the observed alterations, particular emphasis being placed on the biosynthesis of lung surfactant.